Dr. Stacie Jones, the PI, is an assistant professor who completed her pediatric allergy/immunology fellowship in 1994. In this proposal, she outlines a program to study the effects of prolonged beta-agonist treatment on beta2 adrenergic receptor (beta2AR) regulation in patients with asthma. Development of tolerance to beta-agonists has been a significant concern in the treatment of asthma-related bronchospasm. Both in vitro and in vivo studies have demonstrated change in beta2AR density in relation to prolonged beta-agonist exposure. Trafficking of beta2AR to lysosomes for degradation describes the process of down-regulation. Despite its importance in determining responsiveness to beta-agonists, little is known about the molecular mechanisms driving beta2AR down-regulation. This project proposes to use a novel approach employing beta2AR- apidermal growth factor receptor chimeras to define the important molecular determinants and intracellular protein interactions that are responsible for lysosomal sorting and beta2AR down- regulation following prolonged beta-agonist exposure. Information gained in the laboratory will be applied in translational research at the bedside to correlate-the cellular mechanisms responsible for beta2AR down-regulation with genetic polymorphisms of the beta2AR in asthmatics. The central hypothesis of this proposal is that beta2AR down-regulation is driven by specific interaction between a soluble intracellular protein with a beta2AR lysosomal targeting domain and that the rate of down-regulation is modified by polymorphisms in the amino-terminal region of the beta2AR. Employing a series of molecular and cellular biology techniques, the hypothesis will be tested via the following Specific Aims: 1) Identify the functional beta2AR lysosomal targeting domain driving beta2AR trafficking and define the impact of beta2AR amino-terminus polymorphisms on beta2AR down-regulation, 2) Determine the intracellular lysosomal targeting protein(s) responsible for beta2AR sorting to lysosomes, and 3) Assess the clinical relevance of beta2AR polymorphisms in receptor trafficking and down-regulation in asthmatics in the setting of prolonged agonist exposure. Information gained from the proposed studies will advance our knowledge of the association between beta-agonist exposure and beta2AR down-regulation and may led to new approaches in asthma therapeutics. The PI will take advantage of the strong mentoring, protected research time and the outstanding academic resources of the University of Arkansas for Medical Sciences to reach her goal of becoming an independent investigator.